Direct current conversion system and control method thereof

Abstract

The invention discloses a direct current conversion system and a control method thereof, the direct current conversion system comprises a plurality of three-port direct current transformer sub-modules, and the input negative end and the output positive end of each sub-module are connected to form a common end. The input ends of the sub-modules are connected in series, and the output end of the last sub-module can be used as the output end of the converter to realize high transformation ratio voltage reduction; the output ends of all the sub-modules are connected in series, and the input end of the first sub-module can serve as the input end of the converter to achieve high-transformation-ratio boosting; and each sub-module comprises an inverter circuit, a resonance circuit, a high-frequency transformer and a rectification circuit. According to the invention, a high-insulation transformer is not needed; voltage sharing of the high-voltage sides of the sub-modules is easy to realize; and the problems that the impact current is large when a sub-module bypasses due to a fault, a sub-module controller cannot send sub-module state information to a main controller after an input capacitor is powered down, a bypass switch malfunctions after the input capacitor is powered down, and the voltage of the input capacitor is diverged during starting are solved.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a self-equalizing high-DC conversion ratio DC converter based on a three-port DC transformer and a control method thereof. Background technique [0002] In high-voltage DC generators, medical power supplies and other low-voltage input and high-voltage output applications, as well as medium-voltage DC distribution networks, submarine observation network power supply systems and other high-voltage input and low-voltage output applications, DC converters with high DC conversion ratios are key equipment for power transmission. one. High DC conversion ratio DC converters in low voltage input and high voltage output applications often adopt a modular input parallel output series structure, and high DC conversion ratio DC converters in high voltage input and low voltage output applications often adopt a modular input series output parallel structure. In the above two structur...

AI Technical Summary

Problems solved by technology

Compared with conventional transformers, the leakage inductance and distributed capacitance of high-insulation transformers are more difficult to control, and the production cost is relatively high

In the closed-loop control of the output voltage, since the output voltage sampling circuit and the control circuit of the sub-module are located on both sides of the high and low voltage, the control system cannot avoid high-voltage feedback, which greatly increases the structure and control complexity of the converter when the number of sub-modules is large Spend

The input series output parallel structure also has the following problems: 1) the control circuit of the sub-module is difficult to obtain

The energy harvesting method of external power supply requires an expensive high-insulation auxiliary power supply, and often requires an additional uninterruptible power supply to improve the reliability of energy harvesting

The reliability of the self-energy harvesting method is low, and there are many problems when starting up and sub-module bypassing

2) The faulty sub-module is difficult to bypass, and the bypass will generate a huge inrush current instantaneously, which is not conducive to the rapid removal of the fault

3) In the self-energy mode, the power failure of the input capacitor of the sub-module will cause the sub-module controller to fail to send status information to the main controller

5) At start-up, due to the nature of the auxiliary power source with constant power, the voltage of the input capacitor of the sub-module diverges

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